new to forum........

ok, i'm trying this again, my first post was in mustang talk, not tech, some one put wrong thread, which i assume meant i was supposed to post my intro and questions here, in the tech section. i could/nt really tell a difference between tech and talk as the talk is usually about tech....lol....maybe it's just me, to much grease under the fingernails over the yeras has made me mental......go figure.
new to forum, love cars, particularly fords, have always owned older ( 79 and older ) cars, but always wanted a 5.0 and wanted something newer, so last week i purchased a 91 gt with aod. i origunally wanted a stick, but the car was nice, price was right, and i really don't mind automatics after their built. i was going to get a 5 speed and mod it a little and leave it alone, but since i have an aod, i'm going to have to mod it a little more to get it where i want it.
the car has subframe connectors, k&n in stock box with silencer removed, msd blaster coil, under hood brace with corresponding brace underneathm and 3,27 gears ( i have 373's on the way ). equal lenth shorties with h pipe and cats into flowmasters(what else...lol)...
i have done alot of research and am getting my stuff together with this efi stuff, but had some questions to ask. my ultimate goal for this car is to have almost perfect drivability, run mid to late 13's on the engine with the aod, and the air conditioning intact. i must be smog compliant as well.
has anyone used any of the power pluis performance manifolds or tb's i see so cheap???? the manifold is kinda an edelbrock knock off i believe.
next, i need to know how big o parts i can put on this thing relatively stock ( heads and cam and computer ) and not have driveabiltiy issues. for example, i know a 73 mm maf, and a 65 mm tb with the 19 injectors would be ok, however, if and when i upgrade the heads someday, i may wish id gotten a 76 maf and a 70 tb. can i use a 76 and a 70 on it like it is or should i err on the safe side and go smaller??? also, if down the road i need to replace my injectors, can i run 24's on it or are those to big with the stock cam and heads and computer??? i'm trying to not have to buy parts twice as i go along. any coments appreciated........

thanks for the info. i figured the 3.73 would be a better gear as i did'nt want to over do it. i've seen several posts where cars slow down some on the top end as well, i assume thats because while it may be an off line monster, after the rpm's get up their the heads and cam poop out and the engine is just revving, not pulling, although i'm sure the car feels faster it really isnt in the 1/4, for most cars anyway with stock heads cam etc.
as for the heads, i'd assume 600 would be larger valves installed as well, at any rate for 600 i'd most likely decide to spend the extra 3 or 4 hundred and get after,arket heads.
i was curious about the maf because i saw a dyno test for one that was a 76 mm installed on a stock engine that made a decent gain, which was why i wondered if a 76 over a 73 would cause driveability problems.
and as for the aod, i was planning on a transgo shift kit, i see lentech valve bodies are also popular but they are expensive as well. i'm starting to get paranoid about the aod as far as shifting it. i get the feeling your not supposed to manually shift a stock one??? does this stand true with the shift kit? if i get a shift kit should i let it shift by itself or is it then ok to hold it in gear and shift when i want to??
thanks again................